Turbo Underboost (Twin Sequential)
What does MAXXFORCE-P0299-7 mean?
The MAXXFORCE-P0299-7 (MaxxForce) diesel fault code means: Turbo Underboost (Twin Sequential). This is a serious severity code.
Common Symptoms
- Low power
- Black smoke
- Derate
Probable Causes (Ranked by Likelihood)
- Stuck turbo stage valves Likely
- Failed low-pressure turbo Likely
- Cracked charge pipe or CAC Possible
Step-by-Step Diagnostic Procedure
Smoke test charge air system.
Inspect twin turbo assembly for shaft play.
Frequently Asked Questions
What is P0299 on a MaxxForce 7 (6.4L)?
P0299 on a MaxxForce 7 (6.4L) (2007-2013) indicates: Turbo Underboost (Twin Sequential). This is a known fault code on the MaxxForce engine family and typically points to the causes listed above.
Can I drive with P0299 on my MaxxForce?
Only drive short distances to reach a repair facility. Continued operation may cause further damage or progressive derate.
How much does it cost to fix MaxxForce P0299?
Repair cost is typically $400-$4,500 depending on the underlying cause and shop rate. Many MaxxForce faults (especially EGR cooler, head bolt, and VGT repairs) are major expenses that drove fleet owners to repower with Cummins or retire these trucks early.